U.S. patent application number 15/568086 was filed with the patent office on 2018-05-24 for solids based on polyisocvanurate polymers produced under adiabatic conditions.
The applicant listed for this patent is Covestro Deutschland AG. Invention is credited to Dirk ACHTEN, Heiko HOCKE, Hans-Josef LAAS, Dieter MAGER, Mathias MATNER.
Application Number | 20180142056 15/568086 |
Document ID | / |
Family ID | 52997335 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180142056 |
Kind Code |
A1 |
MATNER; Mathias ; et
al. |
May 24, 2018 |
SOLIDS BASED ON POLYISOCVANURATE POLYMERS PRODUCED UNDER ADIABATIC
CONDITIONS
Abstract
The invention relates to a process for producing solids made
from polyisocyanurate plastics, comprising the following steps: (a)
providing a polyisocyanate composition A) which contains oligomeric
polyisocyanates and is low in monomeric polyisocyanates, where the
isocyanurate structure content in the polyisocyanate composition A)
is at least 50 mol %, based on the sum total of the oligomeric
structures from the group consisting of uretdione, isocyanurate,
allophanate, biuret, iminooxadiazinedione and oxadiazinetrione
structure that are present in the polyisocyanate composition A);
(b) catalytically trimerizing the polyisocyanate composition A),
where (i) the catalytic trimerization is conducted at ambient
temperatures of at least 80.degree. C.; (ii) the catalytic
trimerization is conducted within less than 2 hours at least up to
a conversion level at which only at most 20% of the isocyanate
groups originally present in the polyisocyanate composition A) are
present; (iii) the catalytic trimerization takes place under
quasi-adiabatic conditions which are characterized in that the
material temperature at least one juncture is at least 10.degree.
C. above ambient temperature. The invention further relates to
solids made from polyisocyanurate plastic, obtainable by the
process of the invention.
Inventors: |
MATNER; Mathias; (Neuss,
DE) ; ACHTEN; Dirk; (Leverkusen, DE) ; LAAS;
Hans-Josef; (Odenthal, DE) ; HOCKE; Heiko;
(Shanghai, CN) ; MAGER; Dieter; (Leverkusen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Covestro Deutschland AG |
Leverkusen |
|
DE |
|
|
Family ID: |
52997335 |
Appl. No.: |
15/568086 |
Filed: |
April 21, 2016 |
PCT Filed: |
April 21, 2016 |
PCT NO: |
PCT/EP2016/058901 |
371 Date: |
October 20, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 18/755 20130101;
C08G 18/725 20130101; C08G 18/7831 20130101; C08G 18/792 20130101;
C08G 18/022 20130101; C08G 18/225 20130101; C08G 18/73 20130101;
C08G 18/092 20130101; C08G 18/791 20130101; C08G 18/3206
20130101 |
International
Class: |
C08G 18/02 20060101
C08G018/02; C08G 18/09 20060101 C08G018/09; C08G 18/22 20060101
C08G018/22; C08G 18/32 20060101 C08G018/32; C08G 18/72 20060101
C08G018/72; C08G 18/73 20060101 C08G018/73; C08G 18/75 20060101
C08G018/75; C08G 18/78 20060101 C08G018/78; C08G 18/79 20060101
C08G018/79 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2015 |
EP |
15164518.1 |
Claims
1.-13. (canceled)
14. A process for producing solids made from polyisocyanurate
plastics, comprising the following steps: a) providing a
polyisocyanate composition A) which contains oligomeric
polyisocyanates and is low in monomeric polyisocyanates, where the
isocyanurate structure content in the polyisocyanate composition A)
is at least 50 mol %, based on the sum total of the oligomeric
structures from the group consisting of uretdione, isocyanurate,
allophanate, biuret, iminooxadiazinedione and oxadiazinetrione
structure that are present in the polyisocyanate composition A); b)
catalytically trimerizing the polyisocyanate composition A), where
(i) the catalytic trimerization is conducted at ambient
temperatures of at least 80.degree. C.; (ii) the catalytic
trimerization is conducted within less than 2 hours at least up to
a conversion level at which only at most 20% of the isocyanate
groups originally present in the polyisocyanate composition A) are
present; (iii) the catalytic trimerization takes place under
quasi-adiabatic conditions which are characterized in that the
material temperature at at least one juncture is at least
10.degree. C. above ambient temperature.
15. The process according to claim 14, wherein the material
temperature during the catalytic trimerization reaches at least one
temperature above the T.sub.g of the polyisocyanurate plastic
obtained.
16. The process according to claim 14, wherein the catalytic
trimerization is conducted within less than 1 hour or less than 30
minutes at least up to the conversion level specified in step b)
(ii).
17. The process according to claim 14, wherein the conversion level
specified in step b) (ii) is a conversion level at which only at
most 10% of the isocyanate groups originally present in the
polyisocyanate composition A) are present.
18. The process according to claim 14, wherein the conversion level
specified in step b) (ii) is a conversion level at which only at
most 5% of the isocyanate groups originally present in the
polyisocyanate composition A) are present.
19. The process according to claim 14, wherein the polyisocyanate
composition A) consists to an extent of at least 80% by weight,
based on the weight of the polyisocyanate composition A), of
polyisocyanates having exclusively aliphatically and/or
cycloaliphatically bonded isocyanate groups.
20. The process according to claim 14, wherein the polyisocyanate
composition A) consists to an extent of at least 95% by weight,
based on the weight of the polyisocyanate composition A), of
polyisocyanates having exclusively aliphatically and/or
cycloaliphatically bonded isocyanate groups.
21. The process according to claim 14, wherein the polyisocyanate
composition A) consists to an extent of 100% by weight, based on
the weight of the polyisocyanate composition A), of polyisocyanates
having exclusively aliphatically and/or cycloaliphatically bonded
isocyanate groups.
22. The process according to claim 14, wherein the oligomeric
polyisocyanates consist of one or more oligomeric polyisocyanates
formed from 1,4-diisocyanatobutane, 1,5-diisocyanatopentane,
1,6-diisocyanatohexane, isophorone diisocyanate or
4,4'-diisocyanatodicyclohexylmethane or mixtures thereof.
23. The process according to claim 14, wherein the polyisocyanate
composition A) and/or the oligomeric polyisocyanates have/has a
mean NCO functionality of 2.0 to 5.0.
24. The process according to claim 14, wherein the polyisocyanate
composition A) has a content of reactive isocyanate groups of 8% to
28% by weight, based on the weight of the polyisocyanate
composition A).
25. Process according to claim 14, wherein said low in monomeric
polyisocyanates means that the polyisocyanate composition A) has a
content of monomeric polyisocyanates of not more than 20% by weight
based on the weight of the polyisocyanate composition A).
26. The process according to claim 14, wherein said low in
monomeric polyisocyanates means that the polyisocyanate composition
A) has a content of monomeric polyisocyanates of not more than 5%
by weight, based on the weight of the polyisocyanate composition
A).
27. The process according to claim 14, wherein the proportion of
isocyanurate structures in the polyisocyanurate plastic obtained is
at least 20% by weight, based on the weight of the polyisocyanurate
plastic.
28. A solid made from polyisocyanurate plastic, obtainable by the
process according to claim 14.
29. The solid according to claim 28, wherein the polyisocyanurate
plastic has a b* value determined in accordance with DIN 5033 in
the L*a*b* colour space of less than 15.
30. The solid according to claim 28, wherein the polyisocyanurate
plastic has a density of greater than 1.00 g/cm.sup.3.
Description
[0001] The invention relates to a process for producing solids made
from polyisocyanurate plastics, and to the solids made from
polyisocyanurate plastic obtainable therefrom.
[0002] Polymers having polyisocyanurate structure are known for
their high thermal and flame stability. Polyisocyanurate-containing
foams based on aromatic diphenylmethane 4,4'-diisocyanate (MDI),
and also polyether polyols and polyepoxides, are in widespread use
especially as high-performance insulation materials, for example
because of their very low thermal conductivity. See C. E.
Schildknecht and I. Skeist, Polymerization Processes, pp. 665-667,
Wiley, New York (1977). However, the processes for producing such
foams have multiple stages and are time-consuming. The need for
blending with polyols or polyepoxides because of the
incompatibility of the polyisocyanurates formed in their own
starting materials limits the use thereof in high-temperature
applications. Moreover, MDI polyisocyanurate-containing foams, as
is commonly known from aromatic polyurethanes, have only a low
light stability and have a tendency to severe yellowing.
[0003] There has therefore been no lack of attempts to synthesize
polyisocyanurate plastics based on aliphatic light-resistant
isocyanates.
[0004] For example, European Polymer Journal, vol. 16, 147-148
(1980) describes the catalytic trimerization of monomeric
1,6-diisocyanatohexane (HDI) at 40.degree. C. to give a clear
transparent polyisocyanurate plastic free of isocyanate groups. For
this purpose, however, very high catalyst concentrations of
dibutyltin methoxide as trimerization catalyst are required, and
these have a severe adverse effect on the thermal stability and
colour stability of the products. European Polymer Journal, Vol.
16, 831-833 (1980) describes the complete trimerization of
monomeric HDI to give a polyisocyanurate at a temperature of
140.degree. C. using 6% by weight of tributyltin oxide as
catalyst.
[0005] The thesis Theo Flipsen: "Design, synthesis and properties
of new materials based on densely crosslinked polymers for polymer
optical fiber and amplifier applications", Rijksuniversiteit
Groningen, 2000 describes the trimerization of monomeric HDI with a
neodymium/crown ether complex as catalyst. The polyisocyanurate
obtained, which is said to have good optical, thermal and
mechanical properties, was studied in the context of the thesis for
its suitability for optical applications, especially as polymeric
optical fibres. Flipsen gives a detailed description of the
prerequisites for clear non-yellowed polyisocyanurates. Explicit
mention should be made here of avoidance of impurities, water,
dimers, high catalyst concentration and high temperatures at the
start of the reaction. Troublesome side reactions are reaction with
water to give ureas, and of uretdiones to give carbodiimides with
blister formation. According to Flipsen, only under ideal
conditions with a soluble neodymium-crown ether catalyst and a
preliminary reaction at 60.degree. C. or room temperature and
further reaction at temperatures of up to 140.degree. C. are
high-transparency polyisocyanurates having a glass transition
temperature (T.sub.g) of 140.degree. C. obtained over a long period
of greater than 24 h. A disadvantage of the process described is
that it is a multistage process with a complicated reaction regime
with problematic industrial scale implementation.
[0006] Eur. Polym. J. Vol. 18, pp. 549-553, 1982, describes a
process for producing foams, wherein the trimerization is conducted
of 100 g of HDI in the presence of 2% tributyltin oxide at
140.degree. C. over 2 h with evaporative cooling up to conversions
of about 50% and then cooled to 60.degree. C. After adding 2.5% of
an 8% solution of the cobalt naphthenate cocatalyst in DMSO and
adding 8 g of Freon (blowing agent), the reaction commences at
60.degree. C., exploiting the exothermicity of the reaction in
order to increase the temperature of the mixture up to 200.degree.
C. within a few minutes. The mixture is subsequently kept at a
constant temperature of 40.degree. C. overnight. The conversions
thus obtained vary in the region of 90%. The foams thus obtained
were not examined any further for extractable components. The
process described for production of polyisocyanurate foams is not
implementable industrially on a large scale. The expected high HDI
residual monomer content at 50% conversion and the very rapid onset
reaction of the co-catalysed mixture with resulting temperatures of
up to 200.degree. C., in combination with a flashpoint of monomeric
HDI of 140.degree. C., lead to a mixture that cannot be processed
safely under the typical foam production methods as a slabstock or
belt foam.
[0007] The preparation of polyisocyanurates is described in the
prior art mainly proceeding from liquid monomeric diisocyanates
(e.g. stearyl diisocyanate, dodecyl diisocyanate, decyl
diisocyanate, nonyl diisocyanate, octyl diisocyanate, HDI, BDI,
PDI, IPDI, H12MDI, TDI, MDI, NDI, NBDI), of aliphatic and aromatic
nature alike. The exothermicity of the trimerization reaction to
give polyisocyanurates is so high (-75 kJ/mol of NCO) that a
reaction proceeding from monomeric diisocyanates, particularly in
the case of monomeric diisocyanates having a high isocyanate
content (e.g. BDI, PDI, HDI, TIN), typically cannot be effected on
the industrial scale and under adiabatic conditions as typically
occur within solids in strongly exothermic polymerization
processes, but only in small amounts of substance under strict
temperature control.
[0008] An adiabatic change of state is a thermodynamic process in
which a system is converted from one state to another without
exchanging thermal energy with its environment. "Adiabatic
conditions" is understood here to mean that complete dissipation of
the heat of reaction released in the exothermic reaction to the
environment is impossible. Thus, it is typically not possible to
achieve homogeneous conditions in solids, and "adiabatic"
conditions that occur particularly within the solids in the case of
rapid reactions can lead to a local significant increase in
temperature in the case of exothermic reaction. These local
hotspots are extremely critical when the aim is the production of
functionally homogeneous products.
[0009] A further problem is that aromatic monomeric diisocyanates
and many arylaromatic or alicyclic monomeric diisocyanates can be
homo- and co-trimerized only to low conversions. It is often
necessary to add plasticizing or co-dissolving co-reactants.
Otherwise, the reaction stops at high residual isocyanate contents
and typically cloudy and discoloured products are obtained. The use
of plasticizing and co-dissolving co-reactants is disadvantageous
in turn since they lead to less chemically and thermally inert
structural buildup elements such as allophanates, ureas, urethanes,
thiourethanes and oxazolidinones, polyesters, polyethers, and at
high temperatures to uretdiones with subsequent carbodiimidization
and carbon dioxide elimination, and asymmetric isocyanurates. The
production of polyisocyanurates having substantially or exclusively
isocyanurate structures as structural buildup element is therefore
impossible.
[0010] Temperature control in the production of polyisocyanurates
having high conversion levels is of enormous significance since,
because of the high isocyanate contents of the monomeric starting
materials, under adiabatic conditions as typically exist in
trimerizations in solids, and because of the exothermic reaction,
temperatures of more than 300.degree. C., i.e. above the flashpoint
of monomeric HDI of 140.degree. C. and the boiling point of
monomeric HDI of 255.degree. C., and even up to the self-ignition
temperature of HDI of 454.degree. C. can arise. Thus, the high
temperatures can lead to direct breakdown of the products and even
to in situ evaporation and self-ignition of the monomeric
diisocyanates.
[0011] Aside from the occupational hygiene drawbacks resulting from
the monomeric diisocyanates or breakdown products released, the
formation of blisters at relatively high temperatures is very
troublesome. Blisters are formed, for example, because of side
reactions resulting from uretdione formation and subsequent
carbodiimidization with elimination of carbon dioxide. The solids
produced proceeding from monomeric diisocyanates therefore
typically have blisters and thus cannot meet particular
requirements relating to density, electrical insulation
characteristics and mechanical properties.
[0012] Therefore, the only practical applications found by
polyisocyanurates to date have typically been as crosslinking
agents in paint chemistry, the preparation of which involves
stopping the trimerization reaction at low conversions and removing
excess unreacted monomeric diisocyanate. Thus, in the production of
crosslinking agents based on monomeric isocyanurates, proceeding
from aliphatic and mixed aliphatic and aromatic monomeric
diisocyanates, DE 31 00 263; GB 952 931, GB 966 338; U.S. Pat. No.
3,211,703, U.S. Pat. No. 3,330,828 envisage conducting the reaction
either in dilution or only up to low conversion values with very
exact temperature control. There is deliberately no formation here
of crosslinked polyisocyanurate plastics, but only of oligomeric,
soluble products of low viscosity.
[0013] What is common to the abovementioned processes is that the
trimerization is started at low temperatures. High trimerization
temperatures, particularly at the start of the trimerization, can
be controlled only with difficulty proceeding from monomeric
diisocyanates, and lead to considerable side reactions in the form
of uretdiones and carbodiimides, and are thus the cause of blister
formation as a result of carbon dioxide elimination and
discolouration of the product obtained. The only exception is
trimerization in the presence of high concentrations of extremely
slow-acting catalysts, for example tributyltin oxide. The typically
multistage preliminary reactions thus conducted to give low
isocyanate conversions of about 50% at temperatures above
100.degree. C. are too costly and inconvenient for production of
solids from polyisocyanurate plastic and are therefore of no
interest on the industrial scale.
[0014] WO 2015/166983 discloses the use of isocyanurate polymers
for encapsulating LEDs. Whereas the method of the present invention
yields polyisocyanurate plastics with a good optical quality after
curing times of as little as 15 minutes, the process described in
WO 2015/166983 requires curing times of at least hour.
[0015] U.S. Pat. No. 6,133,397 only discloses coatings made by
trimerizing oligomeric polyisocyanates. It does not disclose the
production of solid bodies. What is also common to the processes
described is that they are unsuitable for obtaining
polyisocyanurate plastics in efficient industrial processes,
particularly under adiabatic conditions as typically occur within
solids in strongly exothermic reactions, especially those which are
substantially free of troublesome defects in the form of
discolouration, inhomogeneity and, for example, unwanted blisters.
Nor is it possible in this way, by the processes known from the
prior art, to effect polymerization at elevated temperatures in
open reaction vessels without risking significant release of
monomeric diisocyanates into the environment.
[0016] By contrast, industrially efficient processes are notable
for high conversion rates and high process safety in terms of
occupational hygiene.
[0017] The problem addressed by the invention was therefore that of
developing an efficient industrial process for producing
polyisocyanurates with a high conversion level for solids made from
polyisocyanurate plastics which feature excellent weathering and
chemical stability, and also high thermal stability and good
mechanical properties. Ideally, these solids should lack defects
such as blisters, streaks and discolouration.
[0018] This object is achieved in accordance with the invention by
the process specified in claim 1 for producing solids made from
polyisocyanurate plastics, and by the solids made from
polyisocyanurate plastic that are obtainable by the process and are
specified in claim 11.
[0019] It has been found that, surprisingly, high-functionality
liquid oligomeric polyisocyanurates that are known as crosslinker
raw materials in paint chemistry can be polymerized rapidly and
efficiently even under adiabatic conditions to give
polyisocyanurates having a high conversion level and excellent
chemical stability, and also high thermal stability and good
mechanical properties. When suitable oligomeric polyisocyanurates
are used, even in an adiabatic temperature regime, side reactions
that lead to blisters, inhomogeneities and discolourations are
likewise substantially suppressed. The process of the invention
allows the production of solids made from polyisocyanurates under
adiabatic conditions without breakdown of the materials used or
heating thereof above their flashpoints.
[0020] Compared to the processes known from the prior art for
production of polyisocyanurates based on monomeric diisocyanates,
it is possible in the process of the invention to greatly reduce
environmental pollution with volatile isocyanates, even in the case
of reaction in open vessels, or on surfaces and even at high
trimerization temperatures. This is caused by the fact that
significantly smaller amounts, if any, of monomeric diisocyanates
are present in the reaction mixture. The process of the invention,
even at the gel point, affords homogeneous products having a much
lower concentration of extractable isocyanate-containing
constituents. The gel point is understood to mean the juncture at
which the crosslinking density in the reaction mixture is so far
advanced that the viscosity of the reaction mixture rises abruptly
and the reaction mixture gelates, i.e. no longer significantly
deforms or flows. The processes described in the prior art reach
the gel point only at much higher isocyanate conversions of well
above 50%, since a crosslinking density sufficient for gelation,
proceeding from monomeric diisocyanates having isocyanate
functionalities of less than or equal to two, i.e. less than or
equal to two isocyanate groups per molecule, is statistically
achieved only at higher isocyanate conversions. By contrast, the
use of oligomeric polyisocyanurates having isocyanate
functionalities greater than two, i.e. more than two isocyanate
groups per molecule, statistically results in a high crosslinking
density at a much earlier stage, such that gelation of the reaction
mixture is achieved at lower conversions and hence much earlier.
Furthermore, the processes described in the prior art, even well
after the gel point has been passed, still include extractable
isocyanate-containing constituents.
[0021] Unlike the processes described in the prior art, the
trimerization in the process of the invention can also be conducted
at high temperatures above 80.degree. C. With comparatively short
reaction times below 2 h, it is possible by the process of the
invention to obtain blister-free and transparent products having
low discolouration.
[0022] Particularly advantageously, it is possible to conduct the
trimerization at temperatures above the glass transition point of
the desired products.
[0023] By the process of the invention, it is possible to obtain
solids made from polyisocyanurate plastics which differ in physical
terms, for example in terms of the glass transition temperature,
from the products based on monomeric diisocyanates described in the
prior art. Without wishing to be bound to scientific theories, this
is probably based on structural differences in the nature and
density of the crosslinking in the polyisocyanurate plastic
obtained, which is attributable to the use of oligomeric
polyisocyanates and to the particular reaction regime.
[0024] Advantageous configurations of the invention are specified
in the dependent claims and are elucidated individually
hereinafter, as is the general concept of the invention.
[0025] The invention thus provides a process for producing solids
made from polyisocyanurate plastics, comprising the following
steps: [0026] a) providing a polyisocyanate composition A) which
contains oligomeric polyisocyanates and is low in monomeric
polyisocyanates, where the isocyanurate structure content in the
polyisocyanate composition A) is at least 50 mol %, based on the
sum total of the oligomeric structures from the group consisting of
uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione
and oxadiazinetrione structure that are present in the
polyisocyanate composition A); [0027] b) catalytically trimerizing
the polyisocyanate composition A), where [0028] (i) the catalytic
trimerization is conducted at ambient temperatures of at least
80.degree. C.; [0029] (ii) the catalytic trimerization is conducted
within less than 2 hours at least up to a conversion level at which
only at most 20% of the isocyanate groups originally present in the
polyisocyanate composition A) are present; [0030] (iii) the
catalytic trimerization takes place under quasi-adiabatic
conditions which are characterized in that the material temperature
at least one juncture is at least 10.degree. C. above ambient
temperature.
[0031] The invention further provides the solids made from
polyisocyanurate plastics obtainable by the process.
[0032] The invention described in detail hereinafter is based on
the surprising observation that solids made from novel
polyisocyanurate plastics can be obtained by catalytic
trimerization of low-monomer oligomeric isocyanate compositions A)
at ambient temperatures exceeding 80.degree. C. with short reaction
times of less than 2 h, these having many advantageous properties
and especially being blister-free and transparent and exhibiting
low colour numbers.
[0033] The use of low-monomer oligomeric polyisocyanate
compositions rather than monomeric diisocyanates as starting
materials for production of solids made from polyisocyanurate
plastics additionally has the advantage that, because of the
relatively low isocyanate contents of the oligomeric reactants,
much less heat of reaction has to be dissipated during the curing,
which especially enables a rapid trimerization reaction with short
reaction times of less than 2 h and high temperatures exceeding
80.degree. C. Moreover, the use of low-monomer polyisocyanate
compositions containing oligomeric polyisocyanates as oligomeric
reactants for the trimerization reaction also leads to a novel
crosslinking structure in the polyisocyanurate plastic obtainable,
which distinguishes it structurally from the materials known from
the prior art.
[0034] When mention is made here of "solids", this means a body in
which complete dissipation of the heat that arises in the
trimerization reaction to the environment is impossible because of
its volume and, consequently, local hotspots occur within the
solid. More particularly, a "solid" as used here is a body having,
in its direction of lowest expansion, a thickness of at least 0.5
mm, preferably at least 1 mm, more preferably at least 2 mm. More
particularly, a "solid" as used here is not a film or membrane.
[0035] A "polyisocyanurate plastic" as used here is a plastic
containing polyisocyanurate. It may also consist predominantly or
entirely of a polyisocyanurate. Blends of polyisocyanurates and
other polymers are likewise covered by the term "polyisocyanurate
plastic" as used here.
[0036] When reference is made here to "plastic", this means a
product which is very substantially dimensionally stable at room
temperature--in contrast, for example, to gels or liquids. The term
"plastic" as used here encompasses all standard classes of plastic,
i.e. especially including thermosets, thermoplastics and
elastomers.
[0037] A "polyisocyanurate" as used here is any molecule,
preferably a polymer, having a plurality of isocyanurate structural
units, for example at least ten isocyanurate structural units. A
molecule having a single isocyanurate structural unit can be
referred to as "isocyanurate".
[0038] The characteristic cyclic isocyanate structural unit is
shown in the following structural formula:
##STR00001##
[0039] Isocyanurates and polyisocyanurates can be obtained by
cyclotrimerization of polyisocyanates. The conventionally operated
cyclotrimerization proceeding from monomeric diisocyanates is--as
described above--a strongly exothermic reaction. This can
considerably restrict the use options and the levels of
trimerization that are still achievable industrially and
efficiently.
[0040] The term "polyisocyanate" as used here is a collective term
for compounds containing two or more isocyanate groups in the
molecule (this is understood by the person skilled in the art to
mean free isocyanate groups of the general structure
--N.dbd.C.dbd.O). The simplest and most important representatives
of these polyisocyanates are the diisocyanates. These have the
general structure O.dbd.C.dbd.N--R--N.dbd.C.dbd.O where R typically
represents aliphatic, alicyclic and/or aromatic radicals.
[0041] Because of the polyfunctionality (.gtoreq.2 isocyanate
groups), it is possible to use polyisocyanates to prepare a
multitude of polymers (e.g. polyurethanes, polyureas and
polyisocyanurates) and low molecular weight compounds (for example
those having uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and/or oxadiazinetrione structure).
[0042] When general reference is made here to "polyisocyanates",
this means monomeric and/or oligomeric polyisocyanates. For
understanding of many aspects of the invention, however, it is
important to distinguish between monomeric diisocyanates and
oligomeric polyisocyanates. When reference is made here to
"oligomeric polyisocyanates", this means polyisocyanates formed
from at least two monomeric diisocyanate molecules, i.e. compounds
that constitute or contain a reaction product formed from at least
two monomeric diisocyanate molecules.
[0043] The preparation of oligomeric polyisocyanates from monomeric
diisocyanates is also referred to here as modification of monomeric
diisocyanates. This "modification" as used here means the reaction
of monomeric diisocyanates to give oligomeric polyisocyanates
having uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and/or oxadiazinetrione structure.
[0044] For example, hexamethylene diisocyanate (HDI) is a
"monomeric diisocyanate" since it contains two isocyanate groups
and is not a reaction product of at least two polyisocyanate
molecules:
##STR00002##
[0045] Reaction products which are formed from at least two HDI
molecules and still have at least two isocyanate groups, by
contrast, are "oligomeric polyisocyanates" within the context of
the invention. Representatives of such "oligomeric polyisocyanates"
are, proceeding from monomeric HDI, for example, HDI isocyanurate
and HDI biuret, each of which are formed from three monomeric HDI
units:
##STR00003##
[0046] "Polyisocyanate composition A)" in the context of the
invention refers to the isocyanate component in the initial
reaction mixture. In other words, this is the sum total of all the
compounds in the initial reaction mixture that have isocyanate
groups. The polyisocyanate composition A) is thus used as reactant
in the process of the invention. When reference is made here to
"polyisocyanate composition A)", especially to "providing the
polyisocyanate composition A)", this means that the polyisocyanate
composition A) exists and is used as reactant.
[0047] According to the invention, the polyisocyanate composition
A) used in the trimerization is low in monomers (i.e. low in
monomeric diisocyanates) and contains oligomeric polyisocyanates.
It preferably consists mainly of oligomeric polyisocyanates. In one
embodiment of the invention, the polyisocyanate composition A)
consists entirely or to an extent of 80%, 85%, 90%, 95%, 98%, 99%
or 99.5% by weight, based in each case on the weight of the
polyisocyanate composition A), of oligomeric polyisocyanates. This
content of oligomeric polyisocyanates is based on the
polyisocyanate composition A), meaning that they are not formed,
for instance, as intermediate during the process of the invention,
but are already present in the polyisocyanate composition A) used
as reactant on commencement of the reaction.
[0048] "Low in monomers" and "low in monomeric diisocyanates" are
used synonymously here in relation to the polyisocyanate
composition A).
[0049] Results of particular practical relevance are established
when the polyisocyanate composition A) has a proportion of
monomeric diisocyanates in the polyisocyanate composition A) of not
more than 20% by weight, especially not more than 15% by weight or
not more than 10% by weight, based in each case on the weight of
the polyisocyanate composition A). Preferably, the polyisocyanate
composition A) has a content of monomeric diisocyanates of not more
than 5% by weight, especially not more than 2.0% by weight, more
preferably not more than 1.0% by weight, based in each case on the
weight of the polyisocyanate composition A). Particularly good
results are established when the polymer composition A) is
essentially free of monomeric polyisocyanates. "Essentially free"
means that the content of monomeric polyisocyanates is not more
than 0.5% by weight, based on the weight of the polyisocyanate
composition A).
[0050] It is essential to the invention that the polyisocyanate
composition A) used is a low-monomer composition. In practice, this
can especially be achieved by using, as polyisocyanate composition
A), oligomeric polyisocyanates whose preparation involves, after
the actual modification reaction, at least one further process step
in each case for removal of the unconverted excess monomeric
diisocyanates. In a manner of particular practical relevance, this
monomer removal can be effected by processes known per se,
preferably by thin-film distillation under high vacuum or by
extraction with suitable solvents that are inert toward isocyanate
groups, for example aliphatic or cycloaliphatic hydrocarbons such
as pentane, hexane, heptane, cyclopentane or cyclohexane.
[0051] In a preferred embodiment of the invention, the
polyisocyanate composition A) of the invention is obtained by
modifying monomeric diisocyanates with subsequent removal of
unconverted monomers.
[0052] The processes for producing polyisocyanurate plastics
described in the prior art use very substantially monomeric
diisocyanates as reactants, meaning that pure monomers or
monomer-rich polyisocyanate compositions are catalytically
trimerized. By contrast, the inventive use, i.e. the "provision" of
a low-monomer polyisocyanate composition A) already containing
oligomeric polyisocyanates, surprisingly leads to much lower volume
shrinkage. The relatively low exothermicity of the inventive
reaction additionally allows polyisocyanurate plastics with a high
conversion level to be obtained.
[0053] Preferably, no monomeric diisocyanate is used in the
trimerization reaction of the invention. In a particular embodiment
of the invention, however, the polyisocyanate composition A) may
contain an extra monomeric diisocyanate. In this context, "extra
monomeric diisocyanate" means that it differs from the monomeric
polyisocyanates which have been used for preparation of the
oligomeric polyisocyanates present in the polyisocyanate
composition A). Addition of extra monomeric diisocyanate may be
advantageous for achievement of special technical effects, for
example an exceptional hardness. Results of particular practical
relevance are established when the polyisocyanate composition A)
has a proportion of extra monomeric diisocyanate in the
polyisocyanate composition A) of not more than 20% by weight,
especially not more than 15% by weight or not more than 10% by
weight, based in each case on the weight of the polyisocyanate
composition A). Preferably, the polyisocyanate composition A) has a
content of extra monomeric diisocyanate of not more than 5% by
weight, especially not more than 2.0% by weight, more preferably
not more than 1.0% by weight, based in each case on the weight of
the polyisocyanate composition A).
[0054] In a further particular embodiment of the process of the
invention, the polyisocyanate composition A) may contain monomeric
monoisocyanates or monomeric isocyanates having an isocyanate
functionality greater than two, i.e. having more than two
isocyanate groups per molecule. The addition of monomeric
monoisocyanates or monomeric isocyanates having an isocyanate
functionality greater than two has been found to be advantageous in
order to influence the network density of the polyisocyanurate
plastic. Results of particular practical relevance are established
when the polyisocyanate composition A) has a proportion of
monomeric monoisocyanates or monomeric isocyanates having an
isocyanate functionality greater than two in the polyisocyanate
composition A) of not more than 20% by weight, especially not more
than 15% by weight or not more than 10% by weight, based in each
case on the weight of the polyisocyanate composition A).
Preferably, the polyisocyanate composition A) has a content of
monomeric monoisocyanates or monomeric isocyanates having an
isocyanate functionality greater than two of not more than 5% by
weight, especially not more than 2.0% by weight, more preferably
not more than 1.0% by weight, based in each case on the weight of
the polyisocyanate composition A). Preferably, no monomeric
monoisocyanate or monomeric isocyanate having an isocyanate
functionality greater than two is used in the trimerization
reaction of the invention.
[0055] The low-monomer polyisocyanate composition A) and the
oligomeric polyisocyanates present therein are typically obtained
by modifying simple aliphatic, cycloaliphatic, araliphatic and/or
aromatic monomeric diisocyanates or mixtures of such monomeric
diisocyanates.
[0056] The oligomeric polyisocyanates may, in accordance with the
invention, especially have uretdione, isocyanurate, allophanate,
biuret, iminooxadiazinedione and/or oxadiazinetrione structure. In
one embodiment of the invention, the oligomeric polyisocyanates
have at least one of the following oligomeric structure types or
mixtures thereof:
##STR00004##
[0057] It has been found that, surprisingly, it can be
advantageous, for the reaction regime in the trimerization in the
production of solids, to use a polyisocyanate composition A)
wherein the isocyanurate structure content is at least 50 mol %,
based on the sum total of the oligomeric structures from the group
consisting of uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and oxadiazinetrione structure that are
present in the polyisocyanate composition A). Starting mixtures of
this kind, especially in comparison with trimerization reactions
with polyisocyanate compositions A) wherein the isocyanurate
structure content is less than 50 mol % based on the sum total of
the oligomeric structures from the group consisting of uretdione,
isocyanurate, allophanate, biuret, iminooxadiazinedione and
oxadiazinetrione structure present in the polyisocyanate
composition A), may be converted at high temperatures exceeding
80.degree. C. and short reaction times of less than 2 h to
polyisocyanurate plastics having high conversion levels.
[0058] In a preferred embodiment of the invention, a polymer
composition A) is used wherein the isocyanurate structure content
is at least 60 mol %, preferably 70 mol %, more preferably 80 mol
%, especially preferably 90 mol % and particularly 95 mol %, based
on the sum total of the oligomeric structures from the group
consisting of uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and oxadiazinetrione structure present in the
polyisocyanate composition A).
[0059] In an additional or alternative embodiment, in the process
of the invention, a polyisocyanate composition A) is used which, as
well as the isocyanurate structure, comprises at least one further
oligomeric polyisocyanate having uretdione, biuret, allophanate,
iminooxadiazinedione and oxadiazinetrione structure and mixtures
thereof.
[0060] The proportions of uretdione, isocyanurate, allophanate,
biuret, iminooxadiazinedione and/or oxadiazinetrione structure in
the polyisocyanates A) can be determined, for example, by NMR
spectroscopy. It is possible here with preference to use .sup.13C
NMR spectroscopy, preferably in proton-decoupled form, since the
oligomeric structures mentioned give characteristic signals.
[0061] Irrespective of the underlying oligomeric structure
(uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione
and/or oxadiazinetrione structure), the oligomeric polyisocyanate
composition A) for use in the process of the invention and/or the
oligomeric polyisocyanates present therein preferably have/has a
(mean) NCO functionality of 2.0 to 5.0, preferably of 2.3 to
4.5.
[0062] Results of particular practical relevance are established
when the polyisocyanate composition A) for use in accordance with
the invention has a content of isocyanate groups of 8.0% by weight
to 28.0% by weight, preferably of 14.0% to 25.0% by weight, based
in each case on the weight of the polyisocyanate composition
A).
[0063] Preparation processes for the oligomeric polyisocyanates
having uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and/or oxadiazinetrione structure for use in
accordance with the invention in the polyisocyanate composition A)
are described, for example, in J. Prakt. Chem. 336 (1994) 185-200,
in DE-A 1 670 666, DE-A 1 954 093, DE-A 2 414 413, DE-A 2 452 532,
DE-A 2 641 380, DE-A 3 700 209, DE-A 3 900 053 and DE-A 3 928 503
or in EP-A 0 336 205, EP-A 0 339 396 and EP-A 0 798 299.
[0064] In an additional or alternative embodiment of the invention,
the polyisocyanate composition A) of the invention is defined in
that it contains oligomeric polyisocyanates which have been
obtained from monomeric diisocyanates, irrespective of the nature
of the modification reaction used, with observation of an
oligomerization level of 5% to 45%, preferably 10% to 40%, more
preferably 15% to 30%. "Oligomerization level" is understood here
to mean the percentage of isocyanate groups originally present in
the starting mixture which are consumed during the preparation
process to form uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and/or oxadiazinetrione structures.
[0065] Suitable polyisocyanates for preparation of the
polyisocyanate composition A) for use in the process of the
invention and the oligomeric polyisocyanates present therein are
any desired polyisocyanates obtainable in various ways, for example
by phosgenation in the liquid or gas phase or by a phosgene-free
route, for example by thermal urethane cleavage. Particularly good
results are established when the polyisocyanates are monomeric
diisocyanates. Preferred monomeric diisocyanates are those having a
molecular weight in the range from 140 to 400 g/mol, having
aliphatically, cycloaliphatically, araliphatically and/or
aromatically bonded isocyanate groups, for example
1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI),
1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane,
1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or
2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane,
1,3- and 1,4-diisocyanatocyclohexane,
1,4-diisocyanato-3,3,5-trimethylcyclohexane,
1,3-diisocyanato-2-methylcyclohexane,
1,3-diisocyanato-4-methylcyclohexane,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane
(isophorone diisocyanate; IPDI),
1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4'- and
4,4'-diisocyanatodicyclohexylmethane (H12MDI), 1,3- and
1,4-bis(isocyanatomethyl)cyclohexane,
bis(isocyanatomethyl)norbornane,
4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane,
4,4'-diisocyanato-3,3',5,5'-tetramethyldicyclohexylmethane,
4,4'-diisocyanato-1,1'-bi(cyclohexyl),
4,4'-diisocyanato-3,3'-dimethyl-1,1'-bi(cyclohexyl),
4,4'-diisocyanato-2,2',5,5-tetramethyl-1,1'-bi(cyclohexyl),
1,8-diisocyanato-p-menthane, 1,3-diisocyanatoadamantane,
1,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and
1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate; XDI), 1,3-
and 1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI) and
bis(4-(1-isocyanato-1-methylethyl)phenyl) carbonate, 2,4- and
2,6-diisocyanatotoluene (TDI), 2,4'- and
4,4'-diisocyanatodiphenylmethane (MDI), 1,5-diisocyanatonaphthalene
and any desired mixtures of such diisocyanates. Further
diisocyanates that are likewise suitable can additionally be found,
for example, in Justus Liebigs Annalen der Chemie, volume 562
(1949) p. 75-136.
[0066] Suitable monomeric monoisocyanates which can optionally be
used in the polyisocyanate composition A) are, for example, n-butyl
isocyanate, n-amyl isocyanate, n-hexyl isocyanate, n-heptyl
isocyanate, n-octyl isocyanate, undecyl isocyanate, dodecyl
isocyanate, tetradecyl isocyanate, cetyl isocyanate, stearyl
isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, 3- or
4-methylcyclohexyl isocyanate or any desired mixtures of such
monoisocyanates. An example of a monomeric isocyanate having an
isocyanate functionality greater than two which can optionally be
added to the polyisocyanate composition A) is
4-isocyanatomethyloctane 1,8-diisocyanate (triisocyanatononane;
TIN).
[0067] In one embodiment of the invention, the polyisocyanate
composition A) contains not more than 30% by weight, especially not
more than 20% by weight, not more than 15% by weight, not more than
10% by weight, not more than 5% by weight or not more than 1% by
weight, based in each case on the weight of the polyisocyanate
composition A), of aromatic polyisocyanates. As used here,
"aromatic polyisocyanate" means a polyisocyanate having at least
one aromatically bonded isocyanate group.
[0068] In a preferred embodiment of the process of the invention, a
polyisocyanate composition A) having exclusively aliphatically
and/or cycloaliphatically bonded isocyanate groups is used.
[0069] Aliphatically and cycloaliphatically bonded isocyanate
groups are understood to mean isocyanate groups bonded,
respectively, to an aliphatic and cycloaliphatic hydrocarbyl
radical.
[0070] In another preferred embodiment of the process of invention,
a polyisocyanate composition A) consisting of or comprising one or
more oligomeric polyisocyanates is used, where the one or more
oligomeric polyisocyanates has/have exclusively aliphatically
and/or cycloaliphatically bonded isocyanate groups.
[0071] In a further embodiment of the invention, the polyisocyanate
composition A) consists to an extent of at least 70%, 80%, 85%,
90%, 95%, 98% or 99% by weight, based in each case on the weight of
the polyisocyanate composition A), of polyisocyanates having
exclusively aliphatically and/or cycloaliphatically bonded
isocyanate groups. Practical experiments have shown that
particularly good results can be achieved with polyisocyanate
compositions A) in which the oligomeric polyisocyanates present
therein have exclusively aliphatically and/or cycloaliphatically
bonded isocyanate groups.
[0072] In a particularly preferred embodiment of the process of the
invention, a polyisocyanate composition A) is used which consists
of or comprises one or more oligomeric polyisocyanates, where the
one or more oligomeric polyisocyanates is/are based on
1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI),
1,6-diisocyanatohexane (HDI), isophorone diisocyanate (IPDI) or
4,4'-diisocyanatodicyclohexylmethane (H12MDI) or mixtures
thereof.
[0073] In a further embodiment of the invention, the proportion of
isocyanurate structures in the polyisocyanurate plastic obtained by
the process of the invention is at least 20% by weight, based on
the weight of the polyisocyanurate plastic. The proportion of
isocyanurate structures in the polyisocyanurate plastic obtained
can be determined, for example, via solid-state .sup.13C NMR.
[0074] In a further embodiment of the invention, in the process of
the invention, polyisocyanate compositions A) having a viscosity
greater than 500 mPas and less than 500 000 mPas, preferably
greater than 1000 mPas and less than 300 000 mPas, and more
preferably greater than 1000 mPas less than 200 000 mPas, measured
to DIN EN ISO 3219 at 21.degree. C., are used.
[0075] The polyisocyanurates of the invention are obtainable by
catalytic trimerization by the process of the invention.
"Catalytic" here means in the presence of a suitable catalyst
B).
[0076] Suitable catalysts B) for the process of the invention are
in principle any compounds which accelerate the trimerization of
isocyanate groups to isocyanurate structures. Since isocyanurate
formation, depending on the catalyst used, is frequently
accompanied by side reactions, for example dimerization to give
uretdione structures or trimerization to form iminooxadiazinediones
(called asymmetric trimers), and, in the presence of urethane
groups in the starting polyisocyanate, by allophanatization
reactions, the term "trimerization" in the context of the present
invention is also to be used synonymously for these reactions that
proceed additionally.
[0077] In a particular embodiment, however, trimerization means
that predominantly cyclotrimerizations of at least 50%, preferably
at least 60%, more preferably at least 70% and especially at least
80% of isocyanate groups present in the polyisocyanate composition
A) to give isocyanurate structural units are catalysed. However,
side reactions, especially those to give uretdione, allophanate
and/or iminooxadiazinedione structures, typically occur and can
even be used in a controlled manner in order to advantageously
affect, for example, the T.sub.g value of the polyisocyanurate
plastic obtained.
[0078] Suitable catalysts B) for the process of the invention are,
for example, simple tertiary amines, for example triethylamine,
tributylamine, N,N-dimethylaniline, N-ethylpiperidine, or
N,N'-dimethylpiperazine. Suitable catalysts are also the tertiary
hydroxyalkylamines described in GB 2 221 465, for example
triethanolamine, N-methyldiethanolamine, dimethylethanolamine,
N-isopropyldiethanolamine and 1-(2-hydroxyethyl)pyrrolidine, or the
catalyst systems that are known from GB 2 222 161 and consist of
mixtures of tertiary bicyclic amines, for example DBU, with simple
low molecular weight aliphatic alcohols.
[0079] Likewise suitable as trimerization catalysts B) for the
process of the invention are a multitude of different metal
compounds. Suitable examples are the octoates and naphthenates of
manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium or
lead that are described as catalysts in DE-A 3 240 613, or mixtures
thereof with acetates of lithium, sodium, potassium, calcium or
barium, the sodium and potassium salts of linear or branched
alkanecarboxylic acids having up to 10 carbon atoms that are known
from DE-A 3 219 608, for example of propionic acid, butyric acid,
valeric acid, caproic acid, heptanoic acid, caprylic acid,
pelargonic acid, capric acid and undecylenic acid, the alkali metal
or alkaline earth metal salts of aliphatic, cycloaliphatic or
aromatic mono- and polycarboxylic acids having 2 to 20 carbon atoms
that are known from EP-A 0 100 129, for example sodium or potassium
benzoate, the alkali metal phenoxides known from GB-A 1 391 066 and
GB-A 1 386 399, for example sodium or potassium phenoxide, the
alkali metal and alkaline earth metal oxides, hydroxides,
carbonates, alkoxides and phenoxides known from GB 809 809, alkali
metal salts of enolizable compounds and metal salts of weak
aliphatic or cycloaliphatic carboxylic acids, for example sodium
methoxide, sodium acetate, potassium acetate, sodium acetoacetate,
lead 2-ethylhexanoate and lead naphthenate, the basic alkali metal
compounds complexed with crown ethers or polyether alcohols that
are known from EP-A 0 056 158 and EP-A 0 056 159, for example
complexed sodium or potassium carboxylates, the
pyrrolidinone-potassium salt known from EP-A 0 033 581, the mono-
or polynuclear complex of titanium, zirconium and/or hafnium known
from application EP 13196508.9, for example zirconium tetra-n
butoxide, zirconium tetra-2-ethylhexanoate and zirconium
tetra-2-ethylhexoxide, and tin compounds of the type described in
European Polymer Journal, vol. 16, 147-148 (1979), for example
dibutyltin dichloride, diphenyltin dichloride, triphenylstannanol,
tributyltin acetate, tin octoate, dibutyl(dimethoxy)stannane and
tributyltin imidazolate.
[0080] Further trimerization catalysts suitable for the process of
the invention can be found, for example, in J. H. Saunders and K.
C. Frisch, Polyurethanes Chemistry and Technology, p. 94 ff. (1962)
and the literature cited therein.
[0081] The catalysts B) can be used in the process of the invention
either individually or in the form of any desired mixtures with one
another.
[0082] Preferred catalysts B) are metal compounds of the
aforementioned type, especially carboxylates and alkoxides of
alkali metals, alkaline earth metals or zirconium, in combination
with complexing agents such as crown ethers or polyethylene glycols
or polypropylene glycols, and organic tin compounds of the type
mentioned.
[0083] Particularly preferred trimerization catalysts B) are sodium
and potassium salts of aliphatic carboxylic acids having 2 to 20
carbon atoms in combination with complexing agents such as crown
ethers or polyethylene glycols or polypropylene glycols, and
aliphatically substituted tin compounds.
[0084] Very particularly preferred trimerization catalysts B) for
the process of the invention are potassium acetate in combination
with complexing agents such as crown ethers or polyethylene glycols
or polypropylene glycols and/or tin octoate.
[0085] In the process of the invention, the trimerization catalyst
B) is generally used in a concentration based on the amount of the
polyisocyanate composition A) used of 0.0005% to 5.0% by weight,
preferably of 0.0010% to 2.0% by weight and more preferably of
0.0015% to 1.0% by weight.
[0086] The trimerization catalysts B) that are used in the process
of the invention generally have sufficient solubility in the
polyisocyanate composition A) in the amounts that are required for
initiation of the oligomerization reaction. The catalyst B) is
therefore preferably added to the polyisocyanate composition A) in
neat form.
[0087] Optionally, however, the catalysts B) can also be used
dissolved in a suitable organic solvent to improve their
incorporability. The dilution level of the catalyst solutions can
be freely selected within a very wide range. Catalytically active
catalyst solutions are typically those of a concentration over and
above about 0.01% by weight.
[0088] Suitable catalyst solvents are, for example, solvents that
are inert toward isocyanate groups, for example hexane, toluene,
xylene, chlorobenzene, ethyl acetate, butyl acetate, diethylene
glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene
glycol monomethyl or monoethyl ether acetate, diethylene glycol
ethyl and butyl ether acetate, propylene glycol monomethyl ether
acetate, 1-methoxyprop-2-yl acetate, 3-methoxy-n-butyl acetate,
propylene glycol diacetate, acetone, methyl ethyl ketone, methyl
isobutyl ketone, cyclohexanone, lactones such as
.beta.-propiolactone, .gamma.-butyrolactone, .epsilon.-caprolactone
and .epsilon.-methylcaprolactone, but also solvents such as
N-methylpyrrolidone and N-methylcaprolactam, 1,2-propylene
carbonate, methylene chloride, dimethyl sulphoxide, triethyl
phosphate or any desired mixtures of such solvents.
[0089] If catalyst solvents are used in the process of the
invention, preference is given to using catalyst solvents which
bear groups reactive toward isocyanates and can be incorporated
into the polyisocyanurate plastic. Examples of such solvents are
mono- and polyhydric simple alcohols, for example methanol,
ethanol, n-propanol, isopropanol, n-butanol, n-hexanol,
2-ethyl-1-hexanol, ethylene glycol, propylene glycol, the isomeric
butanediols, 2-ethylhexane-1,3-diol or glycerol; ether alcohols,
for example 1-methoxy-2-propanol, 3-ethyl-3-hydroxymethyloxetane,
tetrahydrofurfuryl alcohol, ethylene glycol monomethyl ether,
ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,
diethylene glycol monomethyl ether, diethylene glycol monoethyl
ether, diethylene glycol monobutyl ether, diethylene glycol,
dipropylene glycol or else liquid higher molecular weight
polyethylene glycols, polypropylene glycols, mixed
polyethylene/polypropylene glycols and the monoalkyl ethers
thereof; ester alcohols, for example ethylene glycol monoacetate,
propylene glycol monolaurate, glycerol mono- and diacetate,
glycerol monobutyrate or 2,2,4-trimethylpentane-1,3-diol
monoisobutyrate; unsaturated alcohols, for example allyl alcohol,
1,1-dimethyl allyl alcohol or oleyl alcohol; araliphatic alcohols,
for example benzyl alcohol; N-monosubstituted amides, for example
N-methylformamide, N-methylacetamide, cyanoacetamide or
2-pyrrolidone, or any desired mixtures of such solvents.
[0090] The polyisocyanurate plastics obtainable by the process of
the invention, even as such, i.e. without addition of appropriate
auxiliaries and additives C), feature very good light stability.
Nevertheless, it is optionally possible to use standard auxiliaries
and/or additives C) as well in the production thereof, for example
standard fillers, UV stabilizers, antioxidants, mould release
agents, water scavengers, slip additives, defoamers, levelling
agents, rheology additives, flame retardants and/or pigments. These
auxiliaries and/or additives C), excluding fillers and flame
retardants, are typically present in the polyisocyanurate plastic
in an amount of less than 10% by weight, preferably less than 5% by
weight, more preferably up to 3% by weight, based on the
polyisocyanate composition A). Flame retardants are typically
present in the polyisocyanurate plastic in amounts of not more than
70% by weight, preferably not more than 50% by weight and more
preferably not more than 30% by weight, calculated as the total
amount of flame retardants used, based on the polyisocyanate
composition A).
[0091] Suitable fillers C.sub.w) are, for example AlOH.sub.3,
CaCO.sub.3, metal pigments such as TiO.sub.2 and further known
standard fillers. These fillers C.sub.w) are preferably used in
amounts of not more than 70% by weight, preferably not more than
50% by weight and more preferably not more than 30% by weight,
calculated as the total amount of fillers used, based on the
polyisocyanate composition A).
[0092] Suitable UV stabilizers C.sub.x) may preferably be selected
from the group consisting of piperidine derivatives, for example
4-benzoyloxy-2,2,6,6-tetramethylpiperidine,
4-benzoyloxy-1,2,2,6,6-pentamethylpiperidine,
bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate,
bis(1,2,2,6,6-pentamethyl-1-4-piperidinyl) sebacate,
bis(2,2,6,6-tetramethyl-4-piperidyl) suberate,
bis(2,2,6,6-tetramethyl-4-piperidyl) dodecanedioate; benzophenone
derivatives, for example 2,4-dihydroxy-, 2-hydroxy-4-methoxy-,
2-hydroxy-4-octoxy-, 2-hydroxy-4-dodecyloxy- or
2,2'-dihydroxy-4-dodecyloxybenzophenone; benzotriazole derivatives,
for example 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol,
2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol,
2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol,
2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol,
2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol,
2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethy-
lbutyl)phenol, isooctyl
3-(3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenylpropiona-
te), 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol,
2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol,
2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol;
oxalanilides, for example 2-ethyl-2'-ethoxy- or
4-methyl-4'-methoxyoxalanilide; salicylic esters, for example
phenyl salicylate, 4-tert-butylphenyl salicylate,
4-tert-octylphenyl salicylate; cinnamic ester derivatives, for
example methyl a-cyano-6-methyl-4-methoxycinnamate, butyl
a-cyano-6-methyl-4-methoxycinnamate, ethyl
a-cyano-6-phenylcinnamate, isooctyl a-cyano-6-phenylcinnamate; and
malonic ester derivatives, such as dimethyl
4-methoxybenzylidenemalonate, diethyl 4-methoxybenzylidenemalonate,
dimethyl 4 butoxybenzylidenemalonate. These preferred light
stabilizers can be used either individually or in any desired
combinations with one another.
[0093] Particularly preferred UV stabilizers C.sub.x) for the
polyisocyanurate plastics producible in accordance with the
invention are those which fully absorb radiation of wavelength
<400 nm. These include, for example, the benzotriazole
derivatives mentioned. Especially preferred UV stabilizers are
2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol,
2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol and/or
2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol.
[0094] It is optionally possible to add one or more of the UV
stabilizers C.sub.x) mentioned by way of example to the
polyisocyanate composition A), preferably in amounts of 0.001% to
3.0% by weight, more preferably 0.01% to 2% by weight, calculated
as the total amount of UV stabilizers used, based on the total
weight of the polyisocyanate composition A).
[0095] Suitable antioxidants C.sub.y) are preferably sterically
hindered phenols, which may be selected preferably from the group
consisting of 2,6-di-tert-butyl-4-methylphenol (ionol),
pentaerythritol
tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate),
octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,
triethylene glycol
bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate,
2,2'-thiobis(4-methyl-6-tert-butylphenol) and 2,2'-thiodiethyl
bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. If required,
they can be used either individually or in any desired combinations
with one another.
[0096] These antioxidants C.sub.y) are preferably used in amounts
of 0.01% to 3.0% by weight, more preferably 0.02% to 2.0% by
weight, calculated as the total amount of antioxidants used, based
on the polyisocyanate composition A).
[0097] The process of the invention can, apart from the small
amounts of any catalyst solvents to be used in addition, be
conducted in a solvent-free manner. Especially in the case of the
inventive use for production of coatings or films, the
polyisocyanate component can optionally also be diluted with
organic solvents to reduce the processing viscosity. Solvents
suitable for this purpose are, for example, the catalyst solvents
that are inert toward isocyanate groups and have already been
described above.
[0098] In the case of the inventive use for production of films,
semi-finished products or mouldings, further auxiliaries and
additives C) added, finally, may also be internal mould release
agents C.sub.z).
[0099] These are preferably the nonionic surfactants containing
perfluoroalkyl or polysiloxane units that are known as mould
release agents, quaternary alkylammonium salts, for example
trimethylethylammonium chloride, trimethylstearylammonium chloride,
dimethylethylcetylammonium chloride, triethyldodecylammonium
chloride, trioctylmethylammonium chloride and
diethylcyclohexyldodecylammonium chloride, acidic monoalkyl and
dialkyl phosphates having 2 to 18 carbon atoms in the alkyl
radical, for example ethyl phosphate, diethyl phosphate, isopropyl
phosphate, diisopropyl phosphate, butyl phosphate, dibutyl
phosphate, octyl phosphate, dioctyl phosphate, isodecyl phosphate,
diisodecyl phosphate, dodecyl phosphate, didodecyl phosphate,
tridecanol phosphate, bis(tridecanol) phosphate, stearyl phosphate,
distearyl phosphate, and any desired mixtures of such mould release
agents.
[0100] Particularly preferred mould release agents C.sub.z) are the
acidic mono- and dialkyl phosphates mentioned, most preferably
those having 8 to 12 carbon atoms in the alkyl radical.
[0101] Internal mould release agents C.sub.z) are used in the
process of the invention, if appropriate, preferably in amounts of
0.01% to 3.0% by weight, more preferably 0.02% to 2.0% by weight,
calculated as the total amount of internal mould release agent
used, based on the polyisocyanate composition A).
[0102] In one embodiment of the process of the invention, a
trimerization catalyst B) or a mixture of different trimerization
catalysts B) is added to the polyisocyanate composition A)
described, optionally under inert gas, for example nitrogen, and
optionally with additional use of the aforementioned solvents and
auxiliaries and additives C), and mixed in homogeneously with the
aid of a suitable mixing unit. The addition of catalyst B) and any
solvent for additional use and auxiliaries and additives C) can
take place in any sequence, successively or in a mixture, in the
above-specified amounts and generally at a temperature of 0 to
100.degree. C., preferably of 15 to 80.degree. C., more preferably
of 20 to 60.degree. C. In a particular embodiment of the invention,
the reaction mixture thus obtained has a pot life, defined as the
time span from the mixing of the polyisocyanate composition A) with
the trimerization catalyst B) until the time at which the viscosity
of the reaction mixture is twice the starting value, of greater
than 10 min at 23.degree. C. This assures both reliable miscibility
and reliable and simple processing without the risk of a reaction
that proceeds in an uncontrolled manner with significant evolution
of heat.
[0103] In an embodiment of the invention of particular practical
relevance, the polyisocyanate composition A) and also the mixture
of catalyst B) and polyisocyanate composition A) are degassed by
customary methods prior to the reaction. Preferably, the
polyisocyanate composition A) of the invention and/or else the
mixture of catalyst B) and polyisocyanate composition A) is
carefully degassed prior to the reaction at temperatures between 10
and 100.degree. C.
[0104] For production of solid bodies, for example semi-finished
products or mouldings, reaction mixtures comprising the catalyst B)
and the polyisocyanate composition A) may be introduced into open
or closed moulds, for example by simple manual pouring, or with the
aid of suitable machinery, for example the low-pressure or
high-pressure machinery which is standard in polyurethane
technology.
[0105] Subsequently, the trimerization reaction can be started by
heating the filled moulds, the optimal mould or ambient
temperature, depending on the catalyst chosen in each case, being
20 to 250.degree. C., preferably from 40 to 200.degree. C., more
preferably from 100 to 190.degree. C. Particularly advantageously,
it is possible to conduct the trimerization at temperatures above
the glass transition point of the desired products. In a particular
embodiment of the invention, the temperature of the reaction
mixture in the course of the reaction reaches more than 80.degree.
C. but remains below 300.degree. C., even locally. In a further
preferred embodiment, the melt temperature during the catalytic
trimerization in the course of the process of the invention reaches
at least one value above the T.sub.g of the polyisocyanurate
plastic obtained.
[0106] The term "melt" refers to reaction mixture during the curing
process. The term "melt temperature" refers to the temperature of
the reaction mixture during the curing process. It is not to be
mistaken as the melting point of the reaction product.
[0107] The glass transition temperatures (T.sub.g) reported here
can be determined by means of dynamic differential calorimetry in
accordance with DIN EN 61006, Method A, using a DSC instrument
calibrated with indium and lead, and conducting three immediately
successive heating runs from -50.degree. C. to +200.degree. C.,
heating rate 20 K/min, with subsequent cooling at a cooling rate of
320 K/min, and using the first heating curve to determine the
values, and determining the temperature at half the height of a
glass transition step as T.sub.g.
[0108] Especially in the case of solids or thick-layered mouldings,
the reaction temperature has an adiabatic component which can lead
to temperature spikes in the reaction material of +5 to
+100.degree. C. compared to the set reaction temperature (i.e.
ambient temperature). The adiabatic component is understood to mean
the reaction enthalpy which is not released to the environment by a
heat transfer but leads to a temperature increase and acceleration
of the reaction in the trimerization mixture. The process of the
invention takes place under at least partly adiabatic conditions,
and for that reason the melt temperature differs by at least
10.degree. C. from the mould or ambient temperature. The melt
temperature may differ especially by at least 20.degree. C.,
25.degree. C., 50.degree. C. or up to 100.degree. C. from the mould
or ambient temperature.
[0109] Depending on the catalyst B) chosen and the reaction
temperature chosen, the trimerization reaction is very
substantially complete, as defined below, after a period of less
than one minute up to several hours. In practice, it has been found
that the trimerization reaction at reaction temperatures of greater
than 80.degree. C. is typically very substantially complete within
less than 2 h. When "reaction temperatures" are being discussed
here, this means the ambient temperature. In a preferred embodiment
of the invention, the trimerization reaction at a reaction
temperature of greater than 80.degree. C. is complete within less
than 1 h, more preferably fewer than 45 min and most preferably
fewer than 30 min. The progress of the reaction can initially still
be determined by titrimetric determination of the NCO content, but
gelation and solidification of the reaction mixture sets in rapidly
with advancing conversion, which makes wet-chemical analysis
methods impossible. The further conversion of isocyanate groups can
then only be monitored by spectroscopic methods, for example by IR
spectroscopy with reference to the intensity of the isocyanate band
at about 2270 cm.sup.-1.
[0110] In a preferred embodiment of the present invention, the
trimerization reaction is completed in less than 1 hour, wherein
the peak temperature within the melt is preferably at least
10.degree. C., more preferably at least 50.degree. C., even more
preferably at least 75.degree. C., even more preferably at least
100.degree. C., even more preferably at least 150.degree. C. and
most preferably at least 200.degree. C. higher than the ambient
temperature.
[0111] In another preferred embodiment of the present invention,
the trimerization reaction is completed in less than 30 minutes,
wherein the peak temperature within the melt is preferably at least
10.degree. C., more preferably at least 50.degree. C., even more
preferably at least 75.degree. C., even more preferably at least
100.degree. C., even more preferably at least 150.degree. C. and
most preferably at least 200.degree. C. higher than the ambient
temperature.
[0112] In yet another preferred embodiment of the present
invention, the trimerization reaction is completed in less than 15
minutes, wherein the peak temperature within the melt is preferably
at least 10.degree. C., more preferably at least 50.degree. C.,
even more preferably at least 75.degree. C., even more preferably
at least 100.degree. C., even more preferably at least 150.degree.
C., and most preferably at least 200.degree. C. higher than the
ambient temperature.
[0113] In yet another preferred embodiment of the present
invention, the trimerization reaction is completed in less than 5
minutes, wherein the peak temperature within the melt is preferably
at least 10.degree. C., more preferably at least 50.degree. C.,
even more preferably at least 75.degree. C., even more preferably
at least 100.degree. C., even more preferably at least 150.degree.
C., and most preferably at least 200.degree. C. higher than the
ambient temperature.
[0114] In yet another preferred embodiment of the present
invention, the trimerization reaction is completed in less than 2
minutes, wherein the peak temperature within the melt is preferably
at least 10.degree. C., more preferably at least 50.degree. C.,
even more preferably at least 75.degree. C., even more preferably
at least 100.degree. C., even more preferably at least 150.degree.
C., and most preferably at least 200.degree. C. higher than the
ambient temperature. The polyisocyanurate plastics of the invention
are preferably polyisocyanurates with high conversion, i.e. those
in which the trimerization reaction to give polyisocyanurate
structures is very substantially complete. A trimerization reaction
to give polyisocyanurate structures can be regarded as "very
substantially complete" in the context of the present invention
when at least 80%, preferably at least 90% and more preferably at
least 95% of the free isocyanate groups originally present in the
polyisocyanate composition A) have reacted. In other words,
preferably only at most 20%, at most 10% and more preferably at
most 5% of the isocyanate groups originally present in the
polyisocyanate composition A) are present in the polyisocyanurate
plastic of the invention. This can be achieved by conducting the
catalytic trimerization in the process of the invention at least up
to a conversion level at which only, for example, at most 20% of
the isocyanate groups originally present in the polyisocyanate
composition A) are present, such that a polyisocyanurate with high
conversion is obtained. The percentage of isocyanate groups still
present can be determined by a comparison of the content of
isocyanate groups in % by weight in the original polyisocyanate
composition A) with the content of isocyanate groups in % by weight
in the reaction product, for example by the aforementioned
comparison of the intensity of the isocyanate band at about 2270
cm.sup.-1 by means of IR spectroscopy.
[0115] In a preferred embodiment, the total content of extractable
isocyanate-containing compounds in the polyisocyanurate plastic of
the invention, based on the polyisocyanate composition A) used, is
less than 1% by weight. The total content of extractable
isocyanate-containing compounds can be effected in a particularly
practicable manner by methods known per se, preferably by
extraction with suitable solvents that are inert toward isocyanate
groups, for example aliphatic or cycloaliphatic hydrocarbons such
as pentane, hexane, heptane, cyclopentane, cyclohexane, toluene or
xylene and subsequent determination of the isocyanate group content
in the extract, for example by IR spectroscopy.
[0116] In another preferred embodiment, the polyisocyanurate
plastics of the invention have a b* value determined in accordance
with DIN 5033 in the L*a*b* colour space of less than 15,
preferably less than 10. Every colour in the L*a*b* colour space is
defined by a colour locus having the Cartesian coordinates {L*, a*,
b*}. The L* axis describes the brightness (luminance) of the colour
with values of 0 to 100. The a* axis describes the green or red
component of a colour, negative values representing green and
positive values representing red. The b* axis describes the blue or
yellow component of a colour, negative values representing blue and
positive values representing yellow. Relatively high positive b*
values therefore indicate significant yellowing which is unwanted
for many applications.
[0117] The polyisocyanurate plastics obtainable by the process of
the invention can advantageously be surface functionalized by
methods known to those skilled in the art. This can be
accomplished, for example, via coating methods or reactive
functionalization, in either case with or without primer.
[0118] With the process of the invention, it is possible in a very
efficient manner to obtain homogeneous, blister-free solids made
from polyisocyanurate plastic. The degree of freedom of a solid
from blisters can be specified via the density. The inventive
solids made from polyisocyanurate plastic especially feature a
density of greater than 1.00 g/cm.sup.3, determined in accordance
with DIN EN ISO 1183-1. The process of the invention especially
affords solids having a density of greater than 1.10 g/cm.sup.3,
preferably greater than 1.15 g/cm.sup.3.
[0119] The process of the invention affords transparent,
yellowing-stable polyisocyanurate plastics which, according to the
nature of the polyisocyanate composition A) used, as well as
isocyanurate structures, optionally contain further oligomeric
structures and feature excellent thermal stabilities.
[0120] The process of the invention enables, in a simple manner,
synthesis of solids made from polyisocyanurate plastics with a high
conversion level at high temperatures with short reaction times by
suitable selection of starting polyisocyanates.
[0121] By contrast with polyisocyanurate plastics which have been
produced proceeding from monomeric diisocyanates, for example HDI,
the process products of the invention are notable, for example, for
a different glass transition temperature (T.sub.g) and considerably
lower volume shrinkage during the curing, and for that reason they
are especially suitable for manufacturing ultrahigh-precision
mouldings. The comparatively low heat of reaction released also
permits the problem-free production of solid large-volume mouldings
without extreme local overheating, which typically leads to
inhomogeneity, side reactions, and hence to discolouration, and
blisters.
[0122] The invention is elucidated in detail hereinafter with
reference to examples.
EXAMPLES
[0123] All percentages are based on weight, unless stated
otherwise.
[0124] The pot life was measured after removal of a 1 ml sample
from the freshly mixed reaction mixture in a Physica MCR 51
rheometer at RT. The pot life has been attained when the starting
viscosity has doubled.
[0125] The NCO contents were determined by titrimetric means to DIN
EN ISO 11909.
[0126] All the viscosity measurements were made with a Physica MCR
51 rheometer from Anton Paar Germany GmbH (DE) to DIN EN ISO
3219.
[0127] The densities of the starting polyisocyanates were
determined to DIN EN ISO 2811, and those of the cured
polyisocyanurate plastics to DIN EN ISO 1183-1.
[0128] The glass transition temperature T.sub.g was determined by
means of DSC (differential scanning calorimetry) with a Mettler DSC
12E (Mettler Toledo GmbH, Giessen, Germany) in accordance with DIN
EN 61006. Calibration was effected via the melt onset temperature
of indium and lead. 10 mg of substance were weighed out in standard
capsules. The measurement was effected by three heating runs from
-50.degree. C. to +200.degree. C. at a heating rate of 20 K/min
with subsequent cooling at a cooling rate of 320 K/min. Cooling was
effected by means of liquid nitrogen. The purge gas used was
nitrogen. The values reported in the table below are each based on
the evaluation of the 1st heating curve, since changes in the
sample in the measurement process at high temperatures are possible
in the reactive systems being examined as a result of the thermal
stress in the DSC. The glass transition temperature T.sub.g
determined was the temperature at half the height of a glass
transition step.
[0129] Shore hardnesses were measured to DIN 53505 with the aid of
a Zwick 3100 Shore hardness tester (from Zwick, Germany) at
23.degree. C. and 50% air humidity.
[0130] The contents (mol %) of the uretdione, isocyanurate,
allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione
structures present in the starting polyisocyanates were calculated
from the integrals of proton-decoupled .sup.13C NMR spectra
(recorded on a Bruker DPX-400 instrument) and are each based on the
sum total of uretdione, isocyanurate, allophanate, biuret,
iminooxadiazinedione and/or oxadiazinetrione structures
present.
[0131] In the case of HDI polyisocyanates, the individual
structural elements have the following chemical shifts (in ppm):
uretdione: 157.1; isocyanurate: 148.4; allophanate: 155.7 and
153.8, biuret: 155.5; iminooxadiazinedione: 147.8, 144.3 and 135.3;
oxadiazinetrione: 147.8 and 143.9.
[0132] IR spectra were recorded on a Spectrum Two FT-IR
spectrometer equipped with an ATR unit from Perkin Elmer, Inc.
[0133] Transmittance was measured with a Byk-Gardner haze-gard plus
instrument according to ASTM D1003 on specimens of thickness 4
mm.
[0134] Discolourations were measured in accordance with DIN 5033
Part 7 on a CM-5 spectrophotometer using specimens of thickness 4
mm without gloss at a viewing angle of 8.degree. and with diffuse
illumination.
[0135] Extractable isocyanates were determined after coarse
comminution of the 4 mm specimen into fragments having a volume of
less than 0.5 cm.sup.3. 10 g were taken from this in the form of
the comminuted fragments and extracted with 50 ml of PA quality
toluene with stirring at 23.degree. C. over the course of 24 h. The
extract was filtered and examined for extractable components
against the toluene used for the extraction by means of GC/MS/EI
testing. The concentration figures result from a GC flame
ionization detection (FID); the compounds found in the GC were
identified by means of MS spectroscopy. The injection volumes were
0.2 microlitre; the method 2301-0291701-04D of the supplier
Currenta GmbH & Co. OHG was used.
[0136] Process of the Invention
[0137] 100 g of the starting polyisocyanate are weighed into a
polypropylene cup together with a catalyst mixture consisting of
0.177 g of potassium acetate, 0.475 g of [18]crown-6 and 3.115 g of
diethylene glycol (sourced from Sigma-Aldrich in PA qualities and
used as supplied), and homogenized at 2750 rpm with the aid of a
Speed-Mixer DAC 150 FVZ (from Hauschild, Germany) for 1 min. 16 g
of the contents of each polypropylene cup are weighed into an
aluminium dish of diameter 6.3 cm and depth 1 cm which, for better
demoulding, had previously been rubbed with 1% soya lecithin W250
in ethyl acetate solution and dried. The aluminium dish thus filled
is heated in a drying cabinet at 180.degree. C. for 15 min. Under
these conditions, the trimerization reaction proceeds under partly
adiabatic conditions, such that the temperature of the "specimen"
is temporarily increased by at least 10.degree. C. compared to the
outside temperature. After cooling to room temperature, the
specimen is demoulded. Specimens of thickness about 0.4 cm are
obtained, which slightly increase in thickness toward the beaker
edge.
[0138] The process of the invention is employed for production both
of inventive and noninventive polyisocyanurate plastics.
[0139] All the polyisocyanates used were sourced from Bayer
Material Science AG, Leverkusen, Germany, and are either
commercially available or can be prepared by methods described in
the patent literature on the basis of readily available monomers
and catalysts.
[0140] Starting Compounds:
[0141] Inventive Starting Polyisocyanate A
[0142] HDI polyisocyanate containing isocyanurate groups, prepared
in accordance with Example 11 of EP-A 330 966, with the alteration
that the catalyst solvent used was 2-ethylhexanol rather than
2-ethylhexane-1,3-diol. The reaction was stopped at an NCO content
of the crude mixture of 42% by adding dibutyl phosphate.
Subsequently, unconverted HDI was removed by thin-film distillation
at a temperature of 130.degree. C. and a pressure of 0.2 mbar.
[0143] NCO content: 23.0%
[0144] NCO functionality: 3.2
[0145] Monomeric HDI: 0.1%
[0146] Viscosity (23.degree. C.): 1200 mPas
[0147] Density (20.degree. C.): 1.17 g/cm.sup.3
[0148] Distribution of the oligomeric structure types:
[0149] Isocyanurate: 89.7 mol %
[0150] Iminooxadiazinedione 2.5 mol %
[0151] Uretdione 2.7 mol %
[0152] Allophanate: 5.1 mol %
[0153] Inventive Starting Polyisocyanate B
[0154] HDI polyisocyanate containing isocyanurate groups, prepared
in accordance with Example 11 of EP-A 330 966. The reaction was
stopped at an NCO content of the crude mixture of 40% by adding
dibutyl phosphate. Subsequently, unconverted HDI was removed by
thin-film distillation at a temperature of 130.degree. C. and a
pressure of 0.2 mbar.
[0155] NCO content: 21.8%
[0156] NCO functionality: 3.4
[0157] Monomeric HDI: 0.1%
[0158] Viscosity (23.degree. C.): 3000 mPas
[0159] Density (20.degree. C.): 1.17 g/cm.sup.3
[0160] Distribution of the oligomeric structure types:
[0161] Isocyanurate: 84.5 mol %
[0162] Iminooxadiazinedione 5.4 mol %
[0163] Uretdione 2.9 mol %
[0164] Allophanate: 7.2 mol %
[0165] Inventive Starting Polyisocyanate C
[0166] Isophorone diisocyanate (IPDI), in accordance with Example 2
of EP-A 0 003 765, was trimerized down to an NCO content of 31.1%
and the excess IPDI was removed by thin-film distillation at
170.degree. C./0.1 mbar. This gave an isocyanurate polyisocyanate
as a virtually colourless solid resin having a melting range of 100
to 110.degree. C.
[0167] NCO content: 16.4%
[0168] NCO functionality: 3.3
[0169] Monomeric IPDI: 0.2%
[0170] 70 parts by weight of the solid IPDI polyisocyanurate were
coarsely comminuted and initially charged in a reaction vessel at
room temperature together with 30 parts by weight of the starting
polyisocyanate A1) under an N.sub.2 atmosphere. To dissolve the
solid resin and homogenize the mixture, it was heated to
100-140.degree. C. and stirred until a virtually clear solution was
obtained. Subsequently, the mixture was cooled to 50.degree. C. and
filtered through a 200.mu. filter.
[0171] NCO content: 21.2%
[0172] NCO functionality: 3.2
[0173] Monomeric IPDI: 0.1%
[0174] Monomeric HDI: 0.1
[0175] Distribution of the oligomeric structure types:
[0176] Isocyanurate: 92.1 mol %
[0177] Iminooxadiazinedione 1.8 mol %
[0178] Uretdione 1.9 mol %
[0179] Allophanate: 4.2 mol %
[0180] Inventive Starting Polyisocyanate D
[0181] The starting polyisocyanate D used was a mixture of 95% by
weight of starting isocyanate B and 5% by weight of hexamethylene
diisocyanate (HDI).
[0182] Inventive Starting Polyisocyanate E
[0183] The starting isocyanate E used was a mixture of 90% by
weight of starting isocyanate B and 10% by weight of
butanediol.
[0184] Noninventive Starting Polyisocyanate F
[0185] HDI polyisocyanate containing biuret groups, prepared in
accordance with the process of EP-A 0 150 769 by reacting 8.2 mol
of HDI with 1.0 mol of water in the presence of 0.05 mol of pivalic
anhydride at a temperature of 125.degree. C. On attainment of an
NCO content of 36.6%, unconverted HDI was removed together with
pivalic anhydride by thin-film distillation at a temperature of
130.degree. C. and a pressure of 0.2 mbar.
[0186] NCO content: 23.0%
[0187] NCO functionality: 3.2
[0188] Monomeric HDI: 0.4%
[0189] Viscosity (23.degree. C.): 2,500 mPas
[0190] Density (20.degree. C.): 1.13 g/cm.sup.3
[0191] Distribution of the oligomeric structure types:
[0192] Biuret: 87.7 mol %
[0193] Noninventive Starting Polyisocyanate G
[0194] HDI polyisocyanate containing isocyanurate and uretdione
groups, prepared by tributylphosphine-catalysed oligomerization in
accordance with Example 1a) of EP-A 0 377 177, with the alteration
that no 2,2,4-trimethylpentane-1,3-diol was used. The reaction was
stopped at an NCO content of 42%, and unconverted HDI was removed
by thin-film distillation at a temperature of 130.degree. C. and a
pressure of 0.2 mbar.
[0195] NCO content: 22.7%
[0196] NCO functionality: 2.2
[0197] Monomeric HDI: 0.3%
[0198] Viscosity (23.degree. C.): 90 mPas
[0199] Density (20.degree. C.): 1.13 g/cm.sup.3
[0200] Distribution of the oligomeric structure types:
[0201] Isocyanurate: 15.6 mol %
[0202] Iminooxadiazinedione 6.3 mol %
[0203] Uretdione 78.1 mol %
[0204] Noninventive Starting Polyisocyanate H
[0205] HDI polyisocyanate containing isocyanurate and
iminooxadiazinedione groups, prepared in accordance with Example 4
of EP-A 0 962 455, by trimerization of HDI using a 50% solution of
tetrabutylphosphonium hydrogendifluoride in isopropanol/methanol
(2:1) as catalyst. The reaction was stopped at an NCO content of
the crude mixture of 43% by adding dibutyl phosphate. Subsequently,
unconverted HDI was removed by thin-film distillation at a
temperature of 130.degree. C. and a pressure of 0.2 mbar.
[0206] NCO content: 23.4%
[0207] NCO functionality: 3.2
[0208] Monomeric HDI: 0.2%
[0209] Viscosity (23.degree. C.): 700 mPas
[0210] Density (20.degree. C.): 1.15 g/cm3
[0211] Distribution of the oligomeric structure types:
[0212] Isocyanurate: 49.9 mol %
[0213] Iminooxadiazinedione 45.3 mol %
[0214] Uretdione 4.8 mol %
[0215] Noninventive Starting Polyisocyanate I
[0216] The starting polyisocyanate I used was hexamethylene
diisocyanate (available from Bayer Material Science AG, Leverkusen,
Germany as Desmodur H).
[0217] Noninventive Starting Polyisocyanate J
[0218] The starting polyisocyanate J used was a polyisocyanate
containing exclusively urethane structure (available as Desmodur XP
2617 from Bayer Material Science AG, Leverkusen, Germany).
[0219] NCO content: 12.5%
[0220] NCO functionality: 2.1
[0221] Monomeric HDI: <0.5%
[0222] Viscosity (23.degree. C.): 4250 mPas
[0223] Density (20.degree. C.): 1.09 g/cm.sup.3
[0224] Distribution of the oligomeric structure types:
[0225] Isocyanurate: 0 mol %
[0226] Urethane: 100 mol %
[0227] The table which follows shows characteristic properties of
the polyisocyanurate plastics obtained or products of the process
of the invention based on inventive (A-E) and noninventive (F-J)*
starting polyisocyanates.
TABLE-US-00001 Starting Extractable poly- Pot Residual isocyanates
iso- life/ Density T.sub.g Transmittance Hardness isocyanate by
(GC/MS) Observation/ cyanate [min] [g/cm.sup.3] [.degree. C.] [%] L
a b Shore D IR [%] [%] explanation A >10 1.18 109 83 94 0.2 6.5
72 <5% 0% Extractable fractions B >10 1.19 106 83 96 0.1 5.9
73 <5% 0% <0.3% found and C >10 1.18 171 85 94 -0.4 5.8 87
<10% 0% identified in the D >10 1.17 108 81 93 0.1 7.1 84
<5% 0% GC/MS spectrum E >10 1.28 53 85 98 -0.1 4.0 82 <5%
0% come from the trimerization catalyst used. F* >10 -- -- -- --
-- -- -- >20% 100% Remains liquid, significant yellowing G*
>10 -- -- -- -- -- -- -- >20% 100% Remains liquid,
significant yellowing H* >10 -- -- -- -- -- -- -- >20%
>50% Remains gel- like/viscous - slight yellowing I* <10
<0.5 -- -- -- -- -- -- -- >5% Reaction starts immediately
after mixing at RT, forming a brown-black discoloured foam, with
temperatures of up to 250.degree. C. measured by means of an IR
camera. J* >10 1.08 19 88 95 -7.2 25.3 38 <5% 0% Very soft
material with significant yellowing *comparative experiments
[0228] The results in the table show that the polyisocyanurate
plastics of the invention based on the inventive starting
polyisocyanates A-E which have been produced by the process of the
invention, by contrast with the noninventive products produced on
the basis of the noninventive starting polyisocyanates F*-I*,
feature a low level of extractable isocyanate-containing
components. For the processing of the inventive starting
polyisocyanates, important pot lives of more than 10 min are
obtained, and the resulting polyisocyanurate plastics exhibit good
mechanical properties and thermal stability, which are indicated by
a hardness of greater than 50 Shore D and a T.sub.g well above
40.degree. C., i.e. well above room temperature. Inventive
polyisocyanurate plastics from the process of the invention, by
comparison with the noninventive products made from the starting
polyisocyanates F*-J*, additionally feature b* values of less than
15 in the L*a*b* colour space and hence a desirable negligibly low
discolouration.
[0229] The noninventive products, which either remain liquid, break
down during the reaction and have a distinct yellow colour or cure
in an uncontrolled and incomplete manner to give foams having a
density of less than 1 g/cm.sup.3, are entirely unsuitable for the
desired use for production of homogeneous high-quality solids.
* * * * *